Method for controlling a hydraulic actuator of an active chassis

Abstract

A method of controlling a hydraulic actuator of an active spring damper element in a vehicle for damping a relative movement between a vehicle structure and a wheel suspension. A hydraulic arrangement is provided for controlling the hydraulic actuator, which includes a hydraulic pump and at least one control valve. In a first method step, a relative movement between the vehicle structure and wheel suspension is detected. A force to be provided by the hydraulic actuator and a volume flow to be provided by the hydraulic pump are determined based on the detected relative movement. Then, a speed of the hydraulic pump is set to provide the volume flow required for the position of the force.

What is claimed is: 
     
       1. A method of controlling a hydraulic actuator of an active spring damper element in a vehicle for damping relative movement between a vehicle structure and a wheel suspension, wherein a hydraulic arrangement comprising a hydraulic pump and at least one control valve is arranged to control the hydraulic actuator, the method comprising the steps of:
 either predicting or detecting a relative movement between the vehicle structure and wheel suspension, 
 determining a force to be applied by the hydraulic pump and the at least one control valve of the hydraulic actuator based on the predicted or detected relative movement, 
 determining a volume flow to be delivered into a first chamber of the hydraulic actuator by the hydraulic pump, said determined volume flow being based on the predicted or detected relative movement, 
 determining a speed of the hydraulic pump to achieve the determined force and the determined volume flow, and 
 applying said determined force by (i) adjusting an opening setting of the at least one control valve, which causes a pressure drop in a second chamber of the hydraulic actuator that is fluidly connected to the at least one control valve, and (ii) operating the hydraulic pump at said determined speed to deliver said determined volume flow into the first chamber of the hydraulic actuator. 
 
     
     
       2. The method according to  claim 1 , wherein the force to be provided is provided by controlling the at least one control valve in the hydraulic actuator. 
     
     
       3. The method according to  claim 1 , wherein the control valve is controlled such that a pressure drop occurs in a hydraulic chamber of the hydraulic actuator. 
     
     
       4. The method according to  claim 1 , wherein the relative movement is already predictively detected. 
     
     
       5. The method according to  claim 1 , wherein a driver input is taken into account when determining the volume flow. 
     
     
       6. The method according to  claim 1 , wherein the step of either predicting or detecting the relative movement between the vehicle structure and wheel suspension comprises predicting the relative movement between the vehicle structure and wheel suspension by analyzing a ground condition ahead of the vehicle. 
     
     
       7. The method according to  claim 1 , wherein the step of either predicting or detecting the relative movement between the vehicle structure and wheel suspension comprises detecting the relative movement between the vehicle structure and wheel suspension using an accelerometer. 
     
     
       8. The method according to  claim 1 , wherein the hydraulic pump is a reversible pump, wherein a first side of the pump is fluidly connected to the first chamber of the hydraulic actuator via a first hydraulic line and a second side of the pump is fluidly connected to the second chamber of the hydraulic actuator via a second hydraulic line. 
     
     
       9. The method according to  claim 8 , wherein a third hydraulic line fluidly interconnects the first and second hydraulic lines, and wherein the at least one control valve is directly and fluidly connected to the third hydraulic line. 
     
     
       10. The method according to  claim 9 , wherein a fourth hydraulic line interconnects the first and second hydraulic lines, and wherein the third and fourth hydraulic lines are fluidly interconnected together by a fifth hydraulic line. 
     
     
       11. The method according to  claim 10 , further comprising a first check valve that is directly and fluidly connected to the fourth hydraulic line. 
     
     
       12. The method according to  claim 11 , wherein a second check valve is directly and fluidly connected to the fourth hydraulic line, and wherein said first and second check valves are disposed on opposite sides of an intersection point connecting the fourth and fifth hydraulic lines. 
     
     
       13. The method according to  claim 10 , wherein a hydraulic reservoir is directly and fluidly connected to the fifth hydraulic line. 
     
     
       14. The method according to  claim 9 , wherein another control valve is directly and fluidly connected to the third hydraulic line, and said at least one control valve and said another control valve are disposed on opposite sides of an intersection point connecting the third and fifth hydraulic lines. 
     
     
       15. The method according to  claim 1 , wherein the adjusting and operating steps are performed at the same time. 
     
     
       16. The method according to  claim 1 , wherein said determined volume flow is set as a function of a driving style that is input by a user of the vehicle. 
     
     
       17. The method according to  claim 1 , wherein the step of determining the force comprises determining a direction of the force and an amplitude of the force.